Head-up displays (referred to as HUD hereinafter) enable the pilot in the cockpit of an airplane to confirm necessary information without turning their eyes to the dash board from the operation direction. Such head up displays are disclosed in U.S. Pat. Nos. 3,737,212 (1973) and 4,218,111 (1980).
Although expensive airplane HUD's are in practical use, they suffer from a problem in that they cannot be easily incorporated in a cockpit because of their large volume. FIG. 9 shows a conventional HUD developed for use for automobiles. This HUD comprises an electronic shutter LCD 34 for displaying information, a light source 35 for applying light to the rear side of the electronic shutter LCD 34 and an optical system 36 for enlarging the display screen of the electronic shutter LCD 34 to form a virtual image in a remote place. A combiner 37 is bonded to the inner side of a front glass 38.
However, in the aforementioned art, the HUD is merely installed on the existing dash board without a spatial commonality with the meters of the instrument cluster. Accordingly, an excess space is required for the HUD, and in general a space where the HUD is installed cannot be easily obtained in a car.
In consideration of the above-mentioned problem of the prior art, it is an object of the present invention to provide an HUD which can be installed in a space which is commonly used with instrument cluster meters three-dimensionally, thereby effectively using the existing space.